1. Field of the Invention
This invention relates generally to fault diagnosis and prognosis systems and, more particularly, to an improved method for fault diagnosis and prognosis using time-stamped diagnostic trouble codes (or fault codes) and Markov chains.
2. Discussion of the Related Art
There is a constant effort in the automotive industry to improve the quality and reliability of vehicles by incorporating fault diagnosis and prognosis features into vehicles. Traditionally, fault diagnosis is performed by a technician who connects a scan tool, or other diagnostic tool (e.g. TECH II™, MDI™), to the vehicle's electronic control unit (ECU). Once connected, diagnostic trouble codes (DTCs) are extracted from the ECU and used to determine what has caused the failure. In some cases, the DTCs alone are not enough to accurately determine the root cause of an issue because one DTC, or a combination of DTCs, can be symptoms for multiple failure modes. In addition, without any information as to when each DTC occurred, it is difficult to ascertain the true cause of a fault.
In recent years, vehicle fault diagnosis has improved with the implementation of on-board diagnostics, which are configured to automatically access vehicle DTCs to provide a vehicle operator or technician with diagnostic information without having to externally connect to the ECU. However, existing techniques are unable to distinguish between two failure modes that have the same DTC signature because they don't utilize the DTC firing time information in a systematic manner.
Therefore, what is needed is a system and method configured to: 1) utilize set time and frequency of DTCs in a statistical method that can diagnose and isolate failure modes, especially ambiguous failure modes (i.e., failure modes having a common DTC signature pattern); 2) diagnose intermittent faults by also modeling when the system does not have any DTCs; and 3) predict the remaining time to next failure state (RTFS) with acceptable confidence limits of a failure mode.